Most computational fluid dynamics (CFD) design procedures follow a direct method, that is, the shape of an object is specified and the CFD design procedure computes a velocity or pressure profile along its surface. This approach is reactive, instead of proactive, since an aesthetically pleasing body shape choice may be aerodynamically inefficient and produce an undesirable velocity and pressure profile. Another body shape design approach is an inverse method which is essentially an iterative use of the direct method. This type of inverse method uses successive guesses to achieve a final shape. At each iteration, the latest shape is analyzed using the direct method and its actual surface velocity or pressure distribution is compared to a desired one. The error is used to construct a correction to the geometry for the next iteration. This approach is one step above trial-and-error, however, with the "corrections" hopefully providing some rationale for making shape changes.
A true inverse method which utilizes a surface vorticity model for designing a shape to meet a desired velocity and pressure profile is presented in the article "A Method for Inverse Aerofoil and Cascade Design by Surface Vorticity", Lewis, R. L., ASME Paper No. 82-GT-154 (1982). This method, however, along with the previously discussed methods, do not address design of a vehicle body shape when two portions of the body surface are in close proximity, and in which one portion has a relatively fixed shape and the other portion has a free shape, that is, one which is changeable. Thus, a vehicle shape design method is needed which provides a vehicle body shape having desired velocity and pressure distribution over separate portions of the body surface having both fixed and free shapes.